The “INESA Lighting Handbook,” ninth edition, is published by the Illuminating Engineering Society of North America and is incorporated by reference here in its entirety. As discussed in chapter seven of that book, a “luminaire” is a device for producing, controlling, and distributing light. It is typically a complete lighting unit consisting of one or more lamps, sockets for positioning and protecting the lamps and for connecting the lamps to a supply of electric power, optical devices for distributing the light, and mechanical components for supporting or attaching the luminaire. Luminaires are also sometimes referred to as “light fixtures.”
“Track lighting” is a term that generally refers to a system that includes at least one such luminaire and a track or rail that is designed to support the luminaire and deliver electric power. For example, the track may be mounted at or near the ceiling surface, recessed into the ceiling, or mounted horizontally or vertically along a wall. So-called track luminaires, or “track lights,” come in many shapes and styles for use with a wide variety of lamps including incandescent, halogen, metal-halide, and fluorescent.
Optical control of track lighting is typically accomplished by positioning the track lights along the track and then aiming the positioned lights at a particular target area. However, other optical control techniques for track lights may utilize reflectors, refractors, diffusers, shades, hoods, cowls, and other devices. “Photometric performance” is a term that broadly refers to the efficiency and effectiveness with which a luminaire delivers light to an intended target and is often described in terms of various light distribution characteristics of a luminare. For example, a “luminous intensity distribution curve” may be used to represent the variation of luminous intensity in a plane through the light center of the luminaire. The term “beam spread” is also used to refer to the angle between two directions in a plane in which the intensity is equal to a certain percentage of the maximum beam intensity. When that intensity is 50% of the maximum intensity through the nominal beam centerline, then the term “beam angle” is also used.
Various mechanisms have been suggested for controlling beam spread and other photometric performance characteristics of track lights and other luminaires. “Marks' Standard Handbook for Mechanical Engineers,” eighth edition, is also incorporated by reference here in its entirety and defines “mechanism” as that part of a machine which contains two or more pieces so arranged that the motion of one compels the motion of the other. According to Marks' Handbook, mechanisms include, but are not limited to linkages, cams, hoists, and/or elliptical trains. A “cam” is usually a plate or cylinder which communicates motion to a follower by means of its edge or a groove cut in its surface. However, other types of cam mechanisms are also known.
For flashlights, beam spread is typically controlled by providing a “focused beam.” This is often accomplished by using a reflector having a generally parabolic configuration and positioning the bulb, or other light source, at or near the focal point of the reflector. Adjustable focussed beams have also been provided using a head which is secured to the flashlight body by means of inter-engaging threads, so that rotation will advance or retract the head in a longitudinal direction relative to the flashlight body. The reflector is then secured to the head while the bulb or light source is fixed to the flashlight body. By moving the head, the bulb can therefore be moved either forward or backward relative to the focal point of the reflector, so as to adjust the focus of the beam.
For example, U.S. Pat. No. 6,045,236 to Cheng et al. is incorporated by reference here and discloses an adjustable focus switch for a flashlight. The bulb holder of the Cheng et al. flashlight includes a base having helical cam slots for engaging mating pins that extend inwardly from a turning ring. As the ring is rotated, the pins move laterally along the helical cam slots. Since the position of the pins is fixed, the base moves axially to accommodate rotation of the pins. The bulb, which is coupled to the base by a retainer ring, thereby moves axially relative to a stationary reflector. A bulb spring maintains contact between the bulb and a battery casing.
U.S. Pat. No. 5,735,594 to Own is also incorporated by reference here and discloses a flashlight including a telescopic assembly for positioning a shade. Spiral grooves in the outer wall of the housing slideably engage bosses that project from the shade. Rotating the shade causes it to move axially until the bulb is withdrawn from the reflective mask so that the flashlight can be used as a traffic signal baton.
In contrast to flashlights, track luminaires often have wires extending from the lamp socket. Rotation and/or translation of these sockets can cause loosening of the wires from the socket terminals, or other damage, that creates electrical shock, and other, hazards.